Menu

Weekly wine defined: Loess

Loess is an important component in most
Washington wines. It’s an aeolian sediment formed by the
accumulation of wind-blown silt, 20 percent or less clay and the
rest equal parts sand and silt that are loosely cemented by calcium
carbonate.

That blend adds to the complexity of our state’s wines. Many of
Washington’s vineyards are located on gentle slopes or on valley
floors. Almost all of these vineyards are planted in loess derived
from sediments deposited by a series of glacial floods, known as
the Missoula floods.

Underneath much of these vineyards is the other reason
Washington is unique in the wine world. The bedrock is basalt
alluvium or just plain basalt. At higher elevations the loess lies
on top of basalt bedrock.

Because basalt is dark colored and dense, it keeps the average
temperatures above average. And basalt keeps the root louse
away.